We have 2 cats (13,10) and a lab that is 8. The 10 year old fat cat has always disliked the dog, doesn't have anything to do with it. The 13 year old tiny cat hissed at the dog, slapped him upside the head, and now sleeps on the dogs head and they clean each other. The dog was introduced to the same way to both cats. Generally the way I've always understood introductions was to separate them by a door, move items back and forth so that they get used to the smell of the other before they are forced to deal with the other. Even trade sides of the door. Outside of that, good luck!